Muhammad Ajaz PhD Scholar, 50th Course: WHAT WE WOULD LIKE LHC TO GIVE US June 27, 2012
Preview:
Citation preview
- Slide 1
- Muhammad Ajaz PhD Scholar, 50th Course: WHAT WE WOULD LIKE LHC
TO GIVE US June 27, 2012
- Slide 2
- Outlines Abstract Motivation The Method Main goal The
Experiment Results from pC- & dC- interaction Discussions
Conclusion 2
- Slide 3
- Abstract we studied nuclear transparency effect using p 12 C-
& d 12 C- interactions @4.2 A GeV/c. half angle ( ) technique
is used which divide the emitted particles in two groups
(incone/outcone) depending on their polar angle in the lab. frame.
The behavior of average characteristics of the incone and the
outcone protons & - mesons are studied separately as a function
of the number of identified protons (N p ) in an event The
transparency observed is divided into three groups: leading effect;
cascade effect; and medium effect. Analyses of the results shows
that coherent interactions of grouped nucleons could be the reason
for the last group of transparency. 3
- Slide 4
- 4 Motivation So study of the Nuclear Transparency in hA &
AA collisions at high energies could help to extract the
information on new phases of the strongly interacting matter as
well as the QCD critical point.
- Slide 5
- Nuclear Transparency (theoretically) T vs. R based on the
parameterization of Bethe from 200800 MeV [H. A. Bethe, Phys.
Rev.57, p. 1125(1940).] r o effective reduced nuclear radius, the
reduced wavelength of the incident particle, z and Z the charge of
the incident particle and the target nucleus, respectively T is the
transparency 5
- Slide 6
- Nuclear Transparency (experimentally) 6 ratio of nuclear cross
section per nucleon to that on a free nucleon. A. Leksanov et al.,
PRL 87, 212301 (2001). ratio of cross section for (e, e p)
scattering measured in nuclear target to the cross section for (e,
e p) in PWIA K. Garrow et al., Phy. Rev. C 66 (2002) 044613 Ratio
of the experimental charge normalized yield divided by the charge
normalized Monte Carlo equivalent yield of target A to that of 1 H
B. Clasie et al., PRL 99, 242502 (2007). Sometimes, due to lack of
appropriate pp data, which enables to calculate R AA, a ratio of
central to peripheral spectra is used (R cp ), on the premise that
ultra peripheral events look very like elementary collisions. F.
Antinori et al., Physics Letters B 623 (2005) 1725 Ratio of the
average characteristics of hadrons in nucleon-nucleus or
nucleus-nucleus collisions as a function of number of protons (N p
) in an event to that of N p = 2 transparency in an experiment
could be defined as an effect at which the characteristics of hA
and AA collisions dont depend on a number of identified protons (N
p ). because N p is connected to the baryon density of matter
- Slide 7
- We define 1/2 from NN interaction at 4.2 A GeV/c which divide
the particle multiplicity in two equal parts half angle ( 1/2 =25 o
: 5 o, 10 o, 15 o, 20 o, 25 o ): Half angle gives incone and
outcone particles with < 1/2 incone particles particles with
> 1/2 outcone particle half angle ( 1/2 ) Technique 7
- Slide 8
- NTNT at high energies using half angle ( ) P.L. Jain, M.Kazuno,
G.Thomas, B.Girard.Phys.Rev.Lett. 33,660,1974; J.I. Cohen, E.M.
Friedlander et al. Lett.Nuovo Cim.,9,337,1974; A.I. Anoshin et al.
Sov. Journal of Nucl. Phys., 27, 5, p.1240-1245, 1978. 8
- Slide 9
- Different mechanisms could be reason of the nuclear
transparency effect [Y. Afek et, al., THC11NI0N - PH - 76 - 87] I.
particle-nucleus collisions is a multistep process 1. Intranuclear
Cascade Models, 2. Leading particle Cascade Models, 3. Energy Flux
Cascade Models, 4. Multiperipheral Regge Type Models, 6. and
various types of Statistical and Hydrodynamical Models II.
particle-nucleus collisions is a single step process F.C. Roesler
and C.B.A. McCusker, Nuovo Cimento 10, 127 (1953). W. Heitler and
C.H. Terreaux, Proc. Phys. Soc. London A66, 929 (1953). S.Z.
Belenkij and L.D. Landau, Nuovo Cimento 3, 15 (1956). D.S. Narayan
and K.V.L. Sarma, Prog, of Theor. Phys. 31, 93 (1964). L.D. Landau
in "Collected Papers of L.D. Landau, Pergamon Press London 1965
(Editor D. Ter Harr). A.M. Baldin, Proceedings of the VI Int. Conf.
on High Energy Physics. A. Dar, MIT Preprint 1972 (unpublished). K.
Gottfried, in "High Energy Physics and Nuclear Structure" North
Holland Publ. Com. 1974 (Editor G. Tibell). A. Dar, Proceeding of
the ICTP Topical Meeting on High Energy Reactions Involving Nuclei,
Trieste 1974 (Editor L. Bertocci). A.Z. Patashinskii, JETP Lett.
19, 338 (1974). G.Berlad, A. Dar and G. Eilam, Phys. Rev. D13, 161
(1976). F. Takagi, Nuovo Cimento Lett. 14, 559 (1975). S.
Fredriksson, Nucl. Phys. B (to be published) [A.M. Baldin,
Proceedings of the VI Int. Conf. on High Energy Physics and Nuclear
Structure, Santa Fe, June 1975 and references therein.] 9
- Slide 10
- Main goal looking for the transparency effect of nuclear matter
To understand whether the effect connects with the first category
of models or with second ones. To reach the goal we used half angle
technique for lightest nuclear system at relativistic
energiessystem 10
- Slide 11
- Nuclear Transparency Effect We have studied the average
characteristics of the secondary charged particles produced in p 12
C- and d 12 C-interactions at 4.2 A GeV /c as a function of N p ;
Experimental Data , and of protons (incone and outcone) , and of +
(incone and outcone) , and of - (incone and outcone) CASCADE Model
, and of protons (incone and outcone) , and of + (incone and
outcone) , and of - (incone and outcone) Fitting to get
quantitative results 11
- Slide 12
- EXPERIMENTAL DATA 12
- Slide 13
- 13
- Slide 14
- p vs N p 14 pCdC The effect is suppressed for Cascade Model as
compared with experiment. It can be explained with some mixture of
the fast + -mesons among these protons in the experiment. The fast
+ -mesons could appear as a result of proton exchange reactions
when leader proton transform to neutron and fast positive pions
through the reactions p n + +
- Slide 15
- 15 p vs N p pC dC
- Slide 16
- pC p vs N p 1. This type of transparency is connected to
leading effect Leading particles are projectiles which could give
some part of their energy during interaction. The particles will
have maximum energy in an event and would be identified in an
experiment as incone particles due to their high energy /low angle.
Due to their high energy they passes very fast through the medium.
That is why medium seems transparent to them. 16
- Slide 17
- 17 - vs N p pCdC
- Slide 18
- 18 - vs N p pC dC We support that these fast and small angle
mesons could be connected with leader nucleons too. They could
appear as a result of charge exchange reactions for the leader
nucleon n p + - and p n + +. It confirmed with the comparison of pC
and dC-data. In pC the difference between model and experimental
data become smaller compare with dC-data due to absent neutron.
This type of transparency may be connected to cascade effect
only.
- Slide 19
- - vs N p pCdC 19
- Slide 20
- - vs N p pC dC 20 Not describe by the cascade model and it
could not be consider as a leader effect because the behavior is
observed for the outer cone - - and + -mesons (low energy secondary
particles with large angle). We consider the result as some signal
on appearance of the transparency which could be connected with
some particular properties of the medium. Because the average
momentum and average transverse momentum of these particles dont
depend on the number of identified protons.
- Slide 21
- 21 pC 0.26 dC 0.28 R~1/ pion radiation area (R) could be
defined ~0.28-0.26 GeV/c the value of R~3.6-3.8 fm The carbon
nucleus radius is roughly R c = R p A 1/3 1.83 fm (here R p ~ 0.8
fm) The diameter of carbon nucleus becomes 3.67 which is the same
as that of the out cone pions radiation area. Discussions
- Slide 22
- 22 The second category included all models that assume that
particle-nucleus collisions is a single step process where a few
nucleons (or partons) in the nucleus interact collectively with the
incident particle. In such models the effective center of mass
energy available for the production of particles is approximately
given by s eff 2m eff P lab, Where m eff is the mass of the system
that interacts collectively with the incident particle, its value
is of the order of a few times the mass of a single nucleon. P lab
is a momentum for the incident particles.
- Slide 23
- 23 Using expression from CTM [Y. Afek, A. Dar and G. Eilam
THC11NI0N - PH - 76 87] for the average multiplicity of secondary
charged particles ( Np ) as a function of the number of fast
protons N p, we can get roughly the number of protons in tube (i p
). The expression: ip and pp are the multiplicity of the secondary
charged particles produced in tube with i p protons and in pp-
interactions respectively so i p ~ 3.0 0.4 in pC and 3.1 0.3 in
dC
- Slide 24
- CONCLUSION 24 5.We observed several cases for which behaviors
of, and didnt depend on the N p some signals on appearance of
nuclear transparency effect. 6.The signals were characterized in
three groups of transparency: I.Transparency due to leading effect
: projectile gives some part of its energy during interaction and
could save other essential part of its energy. The particle will
have maximum energy in an event, very fast passes the medium,
cannot interact more and that is why medium seems transparent for
it. II.Cascade Transparency because data coming from the code could
satisfactorily describes the effects. III.Transparency due to
medium effect. and which could not be explained as a result of
leading effect and as a result of cascade mechanism. Analyses of
the result shows that the collective interaction of grouped
nucleons could be the reason of observed transparency.
- Slide 25
- 25
- Slide 26
- ? 26